# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
#
# Copyright 2002 Ben Escoto <ben@emerose.org>
# Copyright 2007 Kenneth Loafman <kenneth@loafman.com>
#
# This file is part of duplicity.
#
# duplicity is free software; you can redistribute it and/or modify
# under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# duplicity is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with duplicity; if not, write to the Free Software Foundation,
# Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

"""Provides a high-level interface to some librsync functions

This is a python wrapper around the lower-level _librsync module,
which is written in C.  The goal was to use C as little as possible...

"""

import os
from . import _librsync
import types
import array

if os.environ.get('READTHEDOCS') == 'True':
    import mock
    import duplicity
    duplicity._librsync = mock.MagicMock()

blocksize = _librsync.RS_JOB_BLOCKSIZE


class librsyncError(Exception):
    """Signifies error in internal librsync processing (bad signature, etc.)

    underlying _librsync.librsyncError's are regenerated using this
    class because the C-created exceptions are by default
    unPickleable.  There is probably a way to fix this in _librsync,
    but this scheme was easier.

    """
    pass


class LikeFile:
    """File-like object used by SigFile, DeltaFile, and PatchFile"""
    mode = "rb"

    # This will be replaced in subclasses by an object with
    # appropriate cycle() method
    maker = None

    def __init__(self, infile, need_seek=None):
        """LikeFile initializer - zero buffers, set eofs off"""
        self.check_file(infile, need_seek)
        self.infile = infile
        self.closed = self.infile_closed = None
        self.inbuf = ""
        self.outbuf = array.array('c')
        self.eof = self.infile_eof = None

    def check_file(self, file, need_seek=None):
        """Raise type error if file doesn't have necessary attributes"""
        if not hasattr(file, "read"):
            raise TypeError("Basis file must have a read() method")
        if not hasattr(file, "close"):
            raise TypeError("Basis file must have a close() method")
        if need_seek and not hasattr(file, "seek"):
            raise TypeError("Basis file must have a seek() method")

    def read(self, length=-1):
        """Build up self.outbuf, return first length bytes"""
        if length == -1:
            while not self.eof:
                self._add_to_outbuf_once()
            real_len = len(self.outbuf)
        else:
            while not self.eof and len(self.outbuf) < length:
                self._add_to_outbuf_once()
            real_len = min(length, len(self.outbuf))

        return_val = self.outbuf[:real_len].tostring()
        del self.outbuf[:real_len]
        return return_val

    def _add_to_outbuf_once(self):
        """Add one cycle's worth of output to self.outbuf"""
        if not self.infile_eof:
            self._add_to_inbuf()
        try:
            self.eof, len_inbuf_read, cycle_out = self.maker.cycle(self.inbuf)
        except _librsync.librsyncError as e:
            raise librsyncError(str(e))
        self.inbuf = self.inbuf[len_inbuf_read:]
        self.outbuf.fromstring(cycle_out)

    def _add_to_inbuf(self):
        """Make sure len(self.inbuf) >= blocksize"""
        assert not self.infile_eof
        while len(self.inbuf) < blocksize:
            new_in = self.infile.read(blocksize)
            if not new_in:
                self.infile_eof = 1
                assert not self.infile.close()
                self.infile_closed = 1
                break
            self.inbuf += new_in

    def close(self):
        """Close infile"""
        if not self.infile_closed:
            assert not self.infile.close()
        self.closed = 1


class SigFile(LikeFile):
    """File-like object which incrementally generates a librsync signature"""
    def __init__(self, infile, blocksize=_librsync.RS_DEFAULT_BLOCK_LEN):
        """SigFile initializer - takes basis file

        basis file only needs to have read() and close() methods.  It
        will be closed when we come to the end of the signature.

        """
        LikeFile.__init__(self, infile)
        try:
            self.maker = _librsync.new_sigmaker(blocksize)
        except _librsync.librsyncError as e:
            raise librsyncError(str(e))


class DeltaFile(LikeFile):
    """File-like object which incrementally generates a librsync delta"""
    def __init__(self, signature, new_file):
        """DeltaFile initializer - call with signature and new file

        Signature can either be a string or a file with read() and
        close() methods.  New_file also only needs to have read() and
        close() methods.  It will be closed when self is closed.

        """
        LikeFile.__init__(self, new_file)
        if isinstance(signature, types.StringType):
            sig_string = signature
        else:
            self.check_file(signature)
            sig_string = signature.read()
            assert not signature.close()
        try:
            self.maker = _librsync.new_deltamaker(sig_string)
        except _librsync.librsyncError as e:
            raise librsyncError(str(e))


class PatchedFile(LikeFile):
    """File-like object which applies a librsync delta incrementally"""
    def __init__(self, basis_file, delta_file):
        """PatchedFile initializer - call with basis delta

        Here basis_file must be a true Python file, because we may
        need to seek() around in it a lot, and this is done in C.
        delta_file only needs read() and close() methods.

        """
        LikeFile.__init__(self, delta_file)
        if not isinstance(basis_file, types.FileType):
            """ tempfile.TemporaryFile() only guarantees a true file
            object on posix platforms. on cygwin/windows a file-like
            object whose file attribute is the underlying true file
            object is returned.
            """
            if hasattr(basis_file, 'file') and isinstance(basis_file.file, types.FileType):
                basis_file = basis_file.file
            else:
                raise TypeError(_("basis_file must be a (true) file or an object whose "
                                  "file attribute is the underlying true file object"))
        try:
            self.maker = _librsync.new_patchmaker(basis_file)
        except _librsync.librsyncError as e:
            raise librsyncError(str(e))


class SigGenerator:
    """Calculate signature.

    Input and output is same as SigFile, but the interface is like md5
    module, not filelike object

    """
    def __init__(self, blocksize=_librsync.RS_DEFAULT_BLOCK_LEN):
        """Return new signature instance"""
        try:
            self.sig_maker = _librsync.new_sigmaker(blocksize)
        except _librsync.librsyncError as e:
            raise librsyncError(str(e))
        self.gotsig = None
        self.buffer = ""
        self.sigstring_list = []

    def update(self, buf):
        """Add buf to data that signature will be calculated over"""
        if self.gotsig:
            raise librsyncError("SigGenerator already provided signature")
        self.buffer += buf
        while len(self.buffer) >= blocksize:
            if self.process_buffer():
                raise librsyncError("Premature EOF received from sig_maker")

    def process_buffer(self):
        """Run self.buffer through sig_maker, add to self.sig_string"""
        try:
            eof, len_buf_read, cycle_out = self.sig_maker.cycle(self.buffer)
        except _librsync.librsyncError as e:
            raise librsyncError(str(e))
        self.buffer = self.buffer[len_buf_read:]
        self.sigstring_list.append(cycle_out)
        return eof

    def getsig(self):
        """Return signature over given data"""
        while not self.process_buffer():
            pass  # keep running until eof
        return ''.join(self.sigstring_list)
